1. Field of the Invention
The present invention relates to a cleaning apparatus which uses an organic solvent, and more particularly, to a cleaning apparatus which uses the vapor of an organic solvent.
2. Description of the Prior Art
A cleaning method which employs an organic solvent is generally classified either as a dipping method (with the solvent at normal temperature or heated), wherein a material to be cleaned is dipped into the organic solvent, or as a vapor cleaning method, wherein the organic solvent vapor adheres to the material to be cleaned. In the case of the dipping method, when the material is pulled up from a liquid, even if the liquid overflows, oil constituents afloat on the liquids surface stick to the material. This contributes to not only deterioration of detergency, but also to difficulty in collecting solvent adhering to the material. Inevitably, this method increases the amount of solvent consumption. Moreover, with the heating process, heating of the total weight of the solvent is required, which leads to an unfavorable increase in consumption of thermal energy. Hence, the vapor cleaning method is widely used.
A wide variety of vapor cleaning devices (exemplified by Japanese Patent Laid-Open No. 9228/1984, Japanese Utility Model Laid-Open No. 109371/1977 and others) suitable for this method have heretofore been employed. However, such devices involve problems like high manufacturing and operating costs as well as low efficiency and a deteriorated working environment. An arrangement of a conventional apparatus, for example, as illustrated in FIG. 5, is provided with a longitudinally extended cleaning chamber 1 including an entrance 2 formed in an upper portion thereof. An organic solvent 3, such as trichloroethylene or the like, is reserved or stored in a lower portion of cleaning chamber 1; a heating coil 4 is disposed in organic solvent 3, which is intended to evaporate organic solvent 3 thus generating the vapor. A cooling coil 5 for cooling off and condensing the organic solvent vapor is disposed to surround an intermediate portion of cleaning chamber 1. An elevator 7 is provided for moving a material W, which is ascended by actuation of a cylinder 6, between a position facing entrance 2 and a position just above reserved or stored organic solvent 3.
Entrance 2 is equipped with a door 8 and is also placed between a skid rail 9 and a roller conveyor 10 which cooperate to guide material W. Pushers 11a, 11b carry material W in and out of cleaning chamber 1. A liquid receptacle 12 is disposed underneath cooling coil 5, and a separator 13, which collects liquid from receptacle 12, eliminates impurities from and returns liquid into cleaning chamber 1. Also provided is a thermometer 14, a temperature sensor 15 for detecting a temperature of organic solvent 3, and a valve 16 interposed in heating coil 4.
In such an arrangement, organic solvent 3 is heated up beforehand by heating coil 4, and cleaning chamber 1 is filled with organic solvent vapor. Elevator 7, which is in an ascended position, receives material W. Subsequently, elevator 7 is lowered by actuation of cylinder 6, at which time organic solvent vapor comes in contact with a cool surface of material W and thereby is condensed. Fats and oils which are stuck to a surface of material W are cleaned off by condensed organic solvent, thus purifying the surface of material W. Meanwhile, a refrigerant carrier always flows through cooling coil 5; and vapor with which an upper portion of cleaning chamber 1 is filled is so cooled down as to be condensed by means of cooling coil 5. Resultant liquid is collected in liquid receptacle 12, and is then transferred back through separator 13 to a lower portion of cleaning chamber 1. The moment the cleaning operation is finished, elevator 7 rises, and the material W is carried out of cleaning chamber 1 by operating exit pusher 11b, thus completing one cleaning cycle.
In the above-described cleaning apparatus, however, a space available for carrying material W in and out of the upper portion of the cleaning chamber 1 must be prepared. In addition, in order to prevent vapor from volatilizing (leaking or being lost) to the outside via this space, a position in which cooling coil 5 is disposed must gradually be raised. Cleaning chamber 1 inevitably increases in its total height. Since it is necessary to raise material W with elevator 7, there is no choice but to enlarge the inside diameter of cleaning chamber 1 inclusive of space for installing cooling coil 5.
For this reason, cleaning chamber 1 as a whole becomes considerably large in size and hence costs of manufacturing the apparatus, which involves formation of a pit P, grow. Organic solvent used for a cleaning operation must constantly be evaporated, which necessitates a large amount of energy for heating. Undesirably, a vast volume of such energy and a large capacity cleaning chamber combine to bring about still higher running costs. Furthermore, cooling coil 5 must be disposed outside elevator 7 which needs a large space, so that a distance therebetween is extended. This causes a drop in efficiency in collecting organic solvent vapor. Consequently, vapor losses by volatilization increase. Problems then arise: a working environment around the cleaning chamber deteriorates and wasteful consumption of organic solvent increases.